1. Field of the Invention
This invention relates to an apparatus for ion-implantation in elements, the apparatus including a novel lock or transfer means for inserting and removing the elements from a high vacuum space.
2. Prior Art
In the manufacture of semi-conducting components, such as transistors, there is used a semi-conducting material, such as silicon, which is activated. The activation consists in introducing small amounts of another substance, e.g. boron. This additive is to "dope" the elements to a certain depth under the surface, and the depth depends on the purpose and the use of the components which are to be manufactured from the element.
The doping has previously been carried out by the diffusion method. During recent years the so-called ion-implantation method has been used which opens up the possibility of manufacturing new types of components and a substantially greater homogeneity of the finished products.
For the implantation method, an apparatus may be used, having a lock means arranged in one end of a vacuum space, and an ion-source and ion-acceleration means are arranged in the other end. In the ion-source, the dope-material is ionized. The ions are accelerated to the necessary speed and are fired on the element which is situated in the lock means, a surface of the element being exposed toward the inner space of the vacuum container.
In the use of such method, it has been difficult to maintain the high vacuum which is necessary for obtaining a satisfactory result, due to the fact that air leaks into the vacuum space from the outer atmosphere through the lock means.
Apparatus is known which uses a circular disc having a plurality of apertures arranged in a ring, an element which is to be treated being arranged in each of said apertures. Thereafter the lock means is airtightly closed and evacuated, so that all the cavities in the lock means have substantially the same pressure as the vacuum container. When all the elements have been treated, the lock means is opened and the elements are removed.
In order to increase the working speed and the capacity of the apparatus it is desirable that the elements be introduced and removed continuously without stopping the process for replacing a treated set by a new set and evacuating the lock means. However, in such a continuous process lines 24 and 25 will pass into the apertures of the lock means during loading, and will be transported to the aperture leading to the inner space of the vacuum container. If each element is in contact with the vacuum space for ten seconds, a relatively quick interchange of elements and a corresponding quick movement of the slide valve will take place, whereby relatively large amounts of air is introduced into the lock means. A large portion of this air may be removed by evacuating the apertures in the slide valve during the working of the apparatus, but even if the lock means have been manufactured with the utmost accuracy, small spaces between the surfaces of the slide valve and the stationary surfaces will exist through which air may leak from the aperture connected with the outer atmosphere to the aperture connected with the vacuum space in the container.